Welcome To My Presention

• INTRODUCTION

Showrov AhamedEmail:mdshowrovahmed@gmail.comDept. of SWEDaffodil International University

Today’s Topic

• A method is a set of code which is referred to by name and can be called (invoked) at any point in a program simply by utilizing the method's name. Think of a method as a subprogram that acts on data and often returns a value.

• Method In Java

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Table ofContents

• Introduction• About Method

• Example

• Problem

• Method Call

• Parameters

• Usegs Of Class Library

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public class HugeProgram {

public static void main(String [] args) {

1. Codeline2. Codeline3. Codeline…….10000. Codeline

}

}

Problem

Howare you Going

to manage

this Huge

code???

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It's possible that your whole program is implemented

inside the main – method

Result: No one will understand the code!

You have to create the code that is

– Reusable

– You and others can manage it

Well how?

Problem

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How To Divide Your Code

• Best Practics• Use Object Oriented Programming

• Classes, Method, Inheritence

• Lot Of Possiblitics With OOP!

• Concentrate On Methods !• But first let’s concentrate on method !

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What is Method

- A Java method is a collection of statements that are grouped together to perform an operation. When you call the System.out.println() method, for example, the system actually executes several statements in order to display a message on the console.

- Good programmers write in a modular fashion which allows for several programmers to work independently on separate concepts which can be assembled at a later date to create the entire project. The use of methods will be our first step in the direction of modular programming.

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public static − modifier.

Int…. − return type.

methodName − name of the method.

a, b... − formal parameters.

int a, int b….. − list of parameters.

Creating Method

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Built-in: Build-in methods are part of the compiler package,

such as System.out.println( ) and System.exit(0).

User-defined: User-defined methods are created by you, the

programmer. These methods take-on names that you assign to

them and perform tasks that you create.

How to call a method (method calling):

When a method is called, a request is made to perform some action, such as setting a value, printing

statements, returning an answer, etc. The code to call the method contains the name of the method to be

executed and any needed data that the receiving method requires. The required data for a method are

specified in the method's parameter list.

There are two basic types of methods:

You are using methods when you use

System.out.print( ) and System.out.println( ).

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The method name is "readInt" which is defined in the class "Console". Since the method is

defined in the class Console, the word Console becomes the calling object. This particular

method returns an integer value which is assigned to an integer variable named number.

You call a method by writing down the calling object followed by a dot, then the name of the

method, and finally a set of parentheses that may (or may not) have information for the method.

When a method is called, a request is made to perform some action,

such as setting a value, printing statements, returning an answer,

etc. The code to call the method contains the name of the method to be

executed and any needed data that the receiving method requires. The

required data for a method are specified in the method's parameter list.

How to call a method (method calling):

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public class HugeProgram {

public static void main(String [] args) {

doSomething1();

doSomething2();

}

Public static void doSomething1(){

System.out.println(“Hello”);

}

Public static void doSomething2(){

System.out.println(“Java”);

}

}

Methods: Divide Your Code?

Hello Java

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Real Life Example:

I really want to buy gift for my

children. The doll costs 5 euros

and the toy car costs 6 euros. I

have 12 euros, is that enough?

Why didn't I listen to the math

teacher at school? Why didn't I

learn sum – calculations?

Why oh why?

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Real Life Example:

Hello Hello! My name is Mr.Sum and I can sum everything!

Please use my knowledge!

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Real Life Example:

Well Mr Sum. I have a problem Idon't know what is 5 plus 6.

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Don't understand your problem. I only do simple calculations,

I really need to have two integer values to be able to do the sum.

Please just give my two numbers!

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Real Life Example:

Parameters!

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In Java, parameters sent to methods are passed-by-

value: Definition clarification: What is passed "to" a

method is referred to as an "argument". The "type" of

data that a method can receive is referred to as a

"parameter".

Return!

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A method is just a chunk of code that does a particular

job. But methods are set out in a certain way. You have a

method header, and a method body. The header is where

you tell Java what value type, if any, the method

will return (an int value, a double value, a string value,

etc).

Well thanks,

at least I know my numbers and 11 is less than

12,

so great! My children will be very happy!

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Real Life Example:

Mr. Sum?

Parameter Return

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LET'S START CODING

The usage of Class Library

Import java.lang.Math;

Public class Example{

Public static void main(String[]args)

Int maxNumber=Math.max(5,6);

System.out.println(maxNumber);

}

}

Import the class

class

Method

parameter

Mr. Max In Code

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Parameters

public class Example {

public static void main(String [] args) { MyMath.max(5, 10);

}

}

class MyMath {

public static void max(int a, int b) { if(a > b)

System.out.println(a);

else

System.out.println(b);

}

}

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Returnpublic class Example {

public static void main(String [] args) { int

maxNumber = MyMath.max(5, 10); System.out.println(maxNumber);

}

}

class MyMath {

public static int max(int a, int b) { if(a

> b)

return a;

else

return b;

}

}

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Thank You

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• Any Questions?